Apparatus for the electrical transmission of pictures



May 22, 1928. 1,670,757

O.- VON BRONK APPARATUS FOR THE ELECTRICAL TRANSMISSION OF PICTURES Filed June 28, 1926 2 Sheets-Shee t l May 22, 1928.

' O. VON BRONK APPARATUS FOR THE ELECTRICAL TRANSMISSION OF PICTURES Filed June 28, 1926 2 Sheets-Sheet 2 WWW Patented May 22 192 8, I UNITED STATES PATENT OFFICE.

Application filed June 28, 1926, Serial No. 119,088, and in Germany July 8, 1925.

This invention relates to the electrical plates between which is arranged a dielectransmission of pictures and more particu tric, being double refracting under the inlarly to means for carrying out the same -fluence of electrical voltages. Care is taken,

The difliculties which have previously been in this respect that the individual condenser 5 encountered in attempting to effect a very plates are electrically influenced in succesrapid electrical transmission of pictures and sion. The result obtained by means of the the numerous proposals for avoiding these Kerr effect is that the horizontal and also difiiculties are well known from literature on the vertical series of picture elements pass the subject and from patent specifications; through the Kerr cell in succession. If the 65 No difliculties arise in the conversion of frequency of the electrical control of the the picture elements into pulsating electrical one control cell is many times greater than currents by means of photo-cells and the that of the second control cell located at transmission of these impulses along Wires right angles thereto the point of intersection or by radio communication by means of carat any moment ofthe series of picture ele-' 70 rier waves nor in very effective light'control ments travels over the whole surface of the at the receiving station by means of the picture and accordingly decomposes the picmodern high frequency and amplifying deture into small area elements 'or units. vices. The chief obstacles, which arise in Thus the individual lines of the pictureare the construction of practically useful appaelectr -optically controlled by the Kerr ef- 75 ratus for instantaneous 'phototele raphy or feet, i. e. are extinguished or brightened,

"for electrical television, are the ecomposi- Instead of the Kerr effect the so-called tion of the picture at the transmitting sta-. Biot effect can also be used for the electrotion and the synchronous phase-correct reoptical control, that is the phenomenon well composition o'f-the picture elements at the known in physics in which the optical propreceiving station. v erties of a medium transparent to light alter The present invention relates to a new when the medium is subject to mechanical apparatus for the rapid decomposition of a stress, more particularl when it is set in its picture into its individual elements and for natural vibration. Ca ys experiments have the synchronous re-composition of the picshown that piezo-electric crystals can-be ex.- 85

tureelements .at the receivin station, In cited b high frequency alternating current I contradistinctionto a movable eam of light toper orm their natural vibrations or haror equivalent means used for picture decommonies thereof when there is resonance with position in the prior art, according to the the electric oscillations acting on the'crystal; invention ab eam of parallel li ht rays which This piezo-electric efl'ect whlch is especially on pass through oneor more lig t controlling noticeable in quartz but may also be obcells is used, which latter consist of a pluralserved in a number of other crystals, may

ity of'thin layers of an opticall variable also be used, ac cording to the-present'mvenmedium, the optical properties of the sepa- 'tion, for the plcture decomposition and re-- rate layers being electrically controlled in composition by arranging thin laminae of 95 40 sequence. One or' two of these cells are quartz or other suitable mater1al,cut exactly mounted at both the transmittin and re-' axially between the se arate condenser ceiving'stations and are controlle synchro plates ofthe cells inste of us ng. n1tro-- nously-by the same. frequencies. 'I}he"li ht benzole as in the Kerr cell. It 1s essential from the picture to be transmitted ,is ed in this connection that each of the laminae loo 4 through the two light controllin 'cellsof 's'uper-imposedupon each other with inter the transmitter'before it reaches e photomediate coatings, shouldhave' a difierent cell. In a similar manner the rays from'the natural Vlblflti011.' p light-source at the receiving'station infiu- My invention isillustrated 1n the accomenced by the electrical impulses of the photopanying drawings 1n which 106 cellare led through the two control cells "Figure 1 represents. an explanatory. dia- "mounted at that end and are controlled by gram of the picture de-wm m l; and rethese in avsimilar manner-as at the-'transcomposing method-e'mploye accordmg to 'mittin station. the invention,- the diagram representmg The own Kerr efiect of electrical 'doueither the transmitting'or the receiving sta--' 11. ll 'ble-refractioncan' be used to eflect this contion,'asexplained*hereinafter; I a

1 trol -by applying an plurality of condenser Figure 2'repres ents' diagrammatically the a cell shown in Figure 4;

connections of one of the two control cells 3 or 4 in Figure 1 with the source of alternating current in case the Kerr effect is used for these cells;

Figure 3 represents diagrammatically the manner in which the picture transmitted is divided into elements;

Figure 4 represents diagrammatically a control cell 3 or 4 in Figure 1 composed of oscillating crystal layers, together with their circuit connections;

Figure 5 represents a modified form of the 8 represent diagrammatitical layers, the cell 4 with horizontal layers and the analyzer 5 of the Kerr cell and are brought to a focus7 by means of the lens 6. In the transmitting station at this point is located the photo-cell indicated by a rectangle around focus 7. This photo cell is located in an electric circuit, not shown in Figure 1, and transforms the light vibrations into electrical variations of current in the usualmanner, so that the latter may be transmitted also in known manner by means of conductors or without wires to the receiving station.

The decomposition of-the picture 1 into individual point-beams of light acting in succession on the photo-electric cell is effected by providing a passage for the light between the separate layers of the cell by means of suitable electrical control of the 4 layers of the cellin sequence. The succesmuch greater velocity than through sive opening up of the paths for the light through the cell 4 is however effected with 3 so that for each release of one light passage through one layer in the cell 3, all the passages through cell 4 are opened successively through one. layer after th'e'other in the cell '4. Electricity affords a means of carrying out this process in a fraction of a second.

A similar arrangement of the two control cells 3 and 4 as shown in Figure 1 is provided, as has already been mentioned, at the receiving station. The difl'erence between this and the transmitting station consists solely in arranging at the receiving end a source of light, (for example a point filament-tungsten-lamp)' at the focus 7 of the lens 6 instead of a'photo-cell and by conthe cell trolling its light intensity by the photo-cur rents received from the transmitter.

Kerr cell may for instance E be arranged at the point 7 at the receiving station to act as such alight influencing device and would of course have the usual -form of construction as in this case it only has'to control the intensity of a strong source of light by means of the photo-currents arriving from the transmitting station. The rays of light thus altered in intensity at the polnt 7 of the receiving station arerendered parallel by the lens 6 and pass through the Nicol prism 5 which, in the receiving station acts as polarizer. The rays then pass through the two cells 4 and 3 and the Nicol prism 2 which now acts as the analyzer and so reaches the arrow 1 which then -represents the screen. As the cells 4 and 3 at the receiving station areelectrically controlled synchronously respectively with the cells 3 and 4 of the transmitting station, the point of intersection between the horizontal and vertical layers has at any moment at the receiving station always the same relative position as that at the transmitting station and consequently only allows the intensities of light corre- .sponding to that particular point in the original picture to reach the receiving screen.

In the purely diagrammatic examples-of Figure 1 the medium between the parallel condenser plates in-cells 3 and4 (for example .nitrmbenzole or the crystals) is omitted and also for the sake of clearness only five layers of an optically variable medium are shown in these cells. Of course, Y

many more layers are necessary for the decomposition of the picture, for example for a decomposition into 10000 picture elements the two cells each-having 100.layers, which is easily possible to accomplish in practice, by using very thin layers, The polarizers or analyzers 2 and 5 consist preferably not of the natural calc-spar but of artificial crystals of Chile saltpeter (sodium nitrate) which are very suitable and can be produced in large suitable pieces.

'When a special Kerr cell is used at the receiving station at the point 7 in Figure 1 for the instantaneous light control then the analyzer of this cell, or in like manner the polarizer 5 of the device for decomposing the picture, can be omitted as the light proceeding from the Kerr cell 7 is already polarized.

Figure 2 shows the electrical connections of one of the two control cells 3 or 4 with a source of alternating current when the Kerr effect is used for controlling the cell. In this figure the group of parallel lines represents the cell.

One set of condenser plates 0, is in this case conductively connected directly with one pole of the source of alternating current W. A conductor leads from the other pole 1 latesof" the last mentioned ment of the control voltage depends onthe.

'value of the alternating current impedances which are inserted. In order to retain-the amplitudes of the voltages on the separate condenser plates approximately equal, inductive resistances ma be inserted in the leads to the condenser p ates in addi-- tion to the ohmic resistances.

"The light controlling cells need not be arranged exactly. at right angles to one another but it may be of advantage to cross the cells at an oblique an le. The picture received is then compose of elementary units as shown in Figure 3 in which the individual surface elements have -a rhombic .shape. In using condenser plates arranged in this manner a smaller .rotation of the plane of polarization b the voltages applied to the plates is r uire v v :It has] already been mentioned that other electro-optical effects can be used instead of the Kerrefiect for controlling the decompos- 35 ing' cell, for example, oscillating crystals can be used instead of. the nitro-benzole of the Kerr cell. If alternating current is allowed to act-on a cell stem composed of oscillatingcrystals and i f the electrical :lfrequency iscontinually altered within vthe frequency range fixed bythe natural oscillations of the quartz laminae, then only those crystals which areat any time in-re'sonancewith the electrical fr uenc will beset successively into natural vibration. By this means the olarizedrays of light passing para lel through the cell only at this point and at this moment are optically altered'so that v on suitable adjustment of th'e'polarizer and analyzer illumination isv efiected. As the control frequenciesof the secondcell system,

located atright angles to the 'first one, are multiples of the first and can be transmitted by means of modulated carrier -'o'vav es---by wire or wireless methodsto the receiving station together with the picture element frequencies which transmit the light-intensity value, synchronization between the receiver andtransmitteris efiected. .A crystal -'cell of this .accordi'ngito tranformer 12. The crystals 45- 52 located polarized light passing through these crystime unit at which th'edifierent control quencies are her. The oscillations set up by the oscillating circuit 8 of thermionic tube generator 9 are led to the two coatings 10 and 11 of the crystal cell by means 0 the coupling between the coatings are of different lengths as can be seen from the drawing. and consequently have difi'erent natural vibrations.

If the electricaloscillation present in the circuit 8 is continually altered by means 76 of the rotating condenser 13 the individual crystals 5. 12 will, as can be seen from the foregoing, be brought. in succession into natural oscillation so that a control of the tals can be effected and utilized according to the invention. vThe same control takes place in the second cell, which according to Fig. 1 is arranged at right angles to the first, the only difference being that the naturaloscillation's of the crystals and accordingly the control frequencies may be chosen from a different range, and are cyclically applied to the second cell at a rate which is a multiple of the cyclic frequency er re- 1 applied sequentially to the first cel c.

It is not necessary to use special condenser coatings'to separate the individual crystals. Two coatings will suflice for each of the two crosswise disposed decomposing cells between which the whole prism consisting of the separate quartz laminae of different natural oscillations is arranged as is diagranunatir 1 cally shown by Fi re 5 of the drawings whichshows one o the two cells. 'Theindividual crystal laminae mayv be laid not only directly on tog of one another-butmay be compressedwit out detracting from the action of the control frequencies on the optical effect. The individual crystals also oscillate in such a case without any noticeable disadvantageous efl'ect on the adjacent crys tals when the whole crystal system is-compressed to a higher de e. By this means apartv from a small a teration of the natural oscillations of the crystals it only causes" the natural oscillations to be damped the resultant advantage being that the crystal Uri stem becomes more lag free. The reduction of the oscillation period of the individ- .iial crystals, each of which normally requires a very small damping is of importance, particularly in the case of decomposition of the picture into very small units and the con sequently required very high velocities of.

' transmission (television) in order to obtain the invention and which may take the-place in Figure 4 in which the;

' the necessary. rapid optical alteration of the light rays passing through the cell.

Quartz has been found tobe the best piezoelectrieal crystal substance for the cells whichdeoompose the picture. Anisotropic :rdystals of this have however the dis- 1 vantage that they polu'ize' chromatically, Q30

i. e. cause a colour change in the light passing through. In order to avoid this effect caused by the so called rotary dispersion, the two decomposing cells are, according to the present invention, constructed so that the chromatic polarization of the one cell is counteracted by the other cell. This can be obtained, for example, by assembling the horizontal crystal system of laevo-rotatory quartz elements, and the vertical crystal system of dextro-rotary quartz elements as is diagrammatically shown by the arrows in Figure 6. An arrangement of this type shows no chromatic alteration of the white light passing through and allows of a complete extinction and lighting-up of the field of view.

In simplifying the cells for decomposing the picture a further step may be taken by using a coherent or continuous anisotropic crystal, for example a quartz prism converting the whole breadth of the picture, instead of the individual crystal laminae. It is only essential in this case that the crystal structure be such that the individual parallel layers of the crystal can be set in different natural oscillations similarly as in a prism which has been built up.

A piezo-electric crystal may also be used instead of a Kerr cell at point 7 of the receiving station Figure 1 for the light control for differentiating the light intensity value of the individual points of the picture by suitably damping the natural oscillation of the crystal either by pressure or by cementing on an iso-tropic medium (glass).

It is however, not absolutely necessary for a special-element of this type (7, Figure 1) to be used at the receiving station for the control of the light intensities. This special element may be dispensed with according to/the-present invention it one of the two control cells 3, 4 at the receiving station or even both simultaneously undertake the function of the light control ele- Incl 1t for the individual points of the picture. It is merely necessary that at the transmitting end the currents derived from the photo-cell serve to modulate the cell control currents to be transmitted to the receiving station. In thisfcase there only need to be transmitted from the transmitting end to the receiving end:

1. Control currents 'for opening the layers of the one cell; i

2. Control currents for opening the layers of the other cell.

At the receiving end it is then only necessary to use a constant light source and two light controlling cells. The one cell is excited by one of the two variable" control frequencies and the other by the already modulated variable control frequency. Both cell control currents ma also be simultaneously modulated by the p oto-cell currents so that both cells at the receiving end are influenced in their optical conditions by the photo-cell of the transmitting end. A common carrier wave of high frequency is used to transmit the control frequencies. The variable control frequencies are demodulated at the receiving station in a manner well known in radio telephony, for example by using a rectifier.

' The picture transmitting system is' shown diagrammatically in Figures 7 and 8 of the drawings. As the sole purpose is to explain the principle of the invention the illustrations of the high frequency devices are limited to those absolutely necessary. Obviously, all the modulating and amplifying devices-used in high frequency technique can here be suitably used.

Figure 7 shows the picture transmitter and Figure 8 the picture receiver.

In Figure 7 a back coupled thermionic tube generator 31 which supplies the carrier Wave to the aerial 32 connected therewith is used at the source for producing undamped oscillations. The modulating tube 33 which serves to influence the short carrier waves produced by the thermionic tube 31 is located in theanode circuit of the thermionic tube generator 31. 34 and 35 are two additional thermionic tube generators, in the oscillating circuits of which are located rotating condensers 36 and 37. The two tube generators 34 and 35 together with their variable condensers 36 and 37 providethe variable control frequencies necessary for the two cells 38 and 39, which, as can-be seen from the drawings, are coupled respectively with the oscillating circuits of the two generators 34 and. 35 through the'coils 10 and 11. The two condensers 36 and 37 may be connected with one another in such a way that the condenser 37 effects a number of revolutions which is a multiple of that efiected by the condenser 36. The ratio of the two speeds of these condensers is adjusted according to the number of the division lines of the picture to be eflected by the two cells 38 and 39 and depends also on the fineness of division of the picture and on the size of the two cells 38 and 39. In the case where the number of horizontal respectively vertical strips into which the picture is decom sed b each cell is for example 100, the con enser 37 must rotate 100 times faster than the condenser36. The frequency range of these two condensers are also different. They depend on the natural oscillations of the individual crystals in the cells 38 and 39 in which connection it is to be noted that the crystals of the decomposing cell 38 have a different natural oscillation from those of the'cell 39. The control frequencies pro-- means of the two transformers 42 and 43 on the control grids of the modulating thermionic tube 33 which serves to modulate the carrier wave of the transmitter 31. The modulation is however simultaneously altered as can be seen from the drawing, by the photo-cell 14 in such a way that when this cell is obscured from the light rays of the picture to be transmitted and its resistance isinfinitely high, no modulation is effected, whilst when the photo-cell is illuminated the modulating currents are more or less altered according to the degree of illumination. It

is easily seen from the explanation given above, and in considering Figure 1 in con- ]unction with Fig. 7, that the light passing from the plane of the picture 15- throu h the polarizer 16 is controlled by the two ce ls 38 and.39 according to the variable frequencies produced by the two thermionic tube generators 34 and and by this means the picture is first decomposed into its separate elements' The light values of the individual picture elements ass in succession through the analyzer 17 an reach the photocell 14'through. the lens 18. The photo-cell 14 then causes according to these varying light intensity values, as has been described, an alteration of the carrier wave produced by the tube 31 respectively an alteration. of the rid control potential of the tube 33 whic eventually causes the modulation of this wave.

The carrier wavemodulated in this manner arrives at the receiving aerial 19 shown diagrammatically in Figure 8 and is demodu ted or rectified in the detector circuit 20. A control of thetwo "cells 38 and 39 which s effected synchronously with-the control of the two cells 38 and 39 of the transmitter in Figure7 can-then be effected by means of two transformers 21 and 22.

Whilst however, thetwo cells 38 and 39 of the transmitter are completely opened and closed by the controlling action of the two generators 34 and 35 the opening in the case of the cells -'38 *-and 39 of the receiver in Figure 8 is under the control of the control frequency effected by the photo-cell '14.

Accordingly thelight rays produced by the constant source of light 23 and which reach the cells 385' and- 39'through-'the lens 24 and the spacially w1th respect to the particular point on thescreen 27' which they 'areto illuminate but are simultaneously controlled in their light intensity values by-the two cells 38 and 39 so that the true reproduction of the transmitted picture 15 is rendered on the-5 the. picture, having a light' controlling ce consisting of a plurality of thin .laminaeofpane of the screen 27 through the; vanalyzer for directly or indirectly affecting the picture,

polarizer 25 are not only affected trolling action of modulator tube 33 the varying current intensities roduc in photo cell 14 by the varying 1 ht intensities, within t e scope of vt e present invention. 1

I claim- 1. In an apparatus for. the electrical transmission of pictures or the like, means for: de-compcsingmand respectively re-composinlg aving a li ht controlling ce consisting of a pluralitfiof thin laminae of a transparent medium variable as to its optical properties by the ap lication of an electric'potential, an .means or varying said properties in successive cycles through all of said laminae.

2. In an apparatus for the electrical transmission of pictures or the like, means for decomposing and respectively re-composing the picture, having a light controlling cel of a transparent laminated medium variable as to its optical properties in accordance with the frequency of electric potentials applied thereto, each of the'laminae being responsive to .a different frequency', and means within the range to which the group of laminae'contained in the cell is responsive.

4. In an apparatus for the electrical transmission of pictures or the like,\means for de-composing and respectively re-composinfi the picture, having a light controlling ce consisting of -a plurality of thin laminae of quartz, variable as to their optlcal propei ties in accordance with the frequency of frequency, and means for applying cell in successive cycles the frequencies within the range to w ich the group of laminae contained in the cell is res onsive.

5. In an apparatus for t eelectncal trans mission of pictures or the like, means for ide-co osing and respectively re-composin a medium variable as to its optical properties in accordancewith thefrequency of electric potentials applied thereto, each of said laminae being responsive to a different frethe electric potentials applied thereto, each of said laminae being responsive to a difierent.

to the.

quency, thin metallic layers disposed 'between the individual laminae for applying the potentials of varying frequency to said laminae, and means for applying to the cell in successive cycles the frequencies within the range to which the group of laminae contained in the cell its responsive.

6. In an apparatus for the electrical transmission of pictures or the like, means for de-composing and respectively re-composing the picture, having a light controlling cell consisting of a plurality of thin laminae of an optically variable dielectric arranged between electrodes and doubly retracting under the influence of electric potentials applied to said electrodes, and means for varyin the optical character of said laminae in continuous succession through all of said laminae.

7 In an apparatus for the electrical transmission of pictures or the like, means for decomposing and respectively re-composing the picture, havin alight controlling cell consistin of a plurality of thin laminae of a medium variable as to its optical prop,- erties in accordance with the frequency of electric potentials applied thereto, each of said laminae having a different dimension and being accordingly responsive to a different fre uency, means for hpplying electric potentia s to said laminae and means for varying in continuous cycles the frequencies of said potentials ,within the frequency range to which the particulargroup of laminae is responsive.

8. In anapparat us for the electrical transmission of pictures or the like, means for de-composing and respectively re-composing the picture comprising two light controlling cells arranged behind each other in the path of the light rays which compose the picture, each cell consisting of a plurality of thin laminae of a transparent medium variable as to its optical properties by the application of anelectric potential, the lamination of both cells being in the direction of the light rays, the lamination of one cell being inclined at an angle to the lamination in the other cell; and means for varying the optical properties of the laminae in said cells in continuous cyclic succession.

9. In an apparatus for the electrical transmission of'plctures or the like, means for de-composing and respectively re-composing thepicture comprising two light controlling cells arranged behind each other in the path of the light rays which compose the picture, each cell consisting of a plurality of thin laminae of a transparent medium variable as to its optical properties by the application of an electric potential of a particular'fre quency, each lamina respondingto a difierent frequency,

lamination of. one cell being inclinedat an optical the lamination of both cells in the direction of the lightrays, the

angle to the lamination in the other cell, and means for varying the optical properties of the laminae in said cells in continuous cyclic succession.

10. In an apparatus for -the electrical transmission of pictures or the like, means for die-composing and respectively re-composing the picture comprising two light controlling cells arrange-d behind each other in the path of the light rays which compose the picture,- each cell consisting of a. plurality of thin laminae of a transparent medium variable as to its optical properties by the application of an electric potential, the. lamination of both cells being in the direction of the light rays, the lamination of one cell being inclined at right an les to the lamination in the other cell, and means for varying the optical properties of the lamina: in said cells in continuous cyclic succession.

11. In an apparatus for the electrical transmission of pictures or the like, means for tie-composing and respectively re-composing the picture comprising two light controlling cells arranged bchind each other in the path of the li ht rays which compose the picture, each ce 1 consisting of a plurality of thin laminae of a transparent medium variable as to its optical properties by the application of an electric potential, the lamination of both cells being in the direction of the light rays, the lamination. of one cell being inclined at an angle to the lamination in the other cell, and means for varying the optical properties of the laminae in said cells in continuous cyclic succession, the laminae of one cell having an optical characteristic with relation to the laminae in the other cell, such that a characteristic change caused in the light rays which have passed through one cell is compensated when the rays pass through the other cell. v

i 12. In an apparatus for ,the electrical transmission of pictures or the like, means for de-composing and respectively re-composing the icture comprisingtwo light controlling cel s arranged behind each other in the path of the light rays which compose the picture each cell consisting of a plurality of thin laminae of a transparent medium variable as to its optical properties by the application of an electric potential, the lamination of both cells bei the light rays, the lam km the direction of nation of one cell beinginclined at ail-angle to thelaminat-ion in theother cell, and means for varying the properties of the lamina: J in continuous cyclic succession, the'rm edium of which the laminae of one cell are composed being laevo-rotar'y quartz, andthat of which the laminae of the other. cell.are, composed being dextro-rotary. quartz.-; a

13. In an apparatus for transmission of pictures or the like, meags in; said cells i trollin thin laminae-of a transparent medium variable as to its optical properties by the application of an electric potential of a particular frequency, each lamina responding to a different frequency, the lamination of both cells being inthe direction of the light rays and" the lamination of one cell being lnclined at an angle to thelamination in the other cell,

Y time unit a means forapplying in continuous cycles to each cell all frequencies within the range to which the group of laminae contained in the cell is responsive, the number of cycles per plied'to one-cell being a multiple ofnthe num r of cycles applied to the other ce 14. In an apparatus for the electrical transmission of pictures or the like, means for de-composing and respectively re-com- I posing the picture comprising light controlling cells, each cell consisting of a plurality of thin lamina of a transparent medium variable as to its optical operties' by the application of an electrigl potential, and means for varying said properties in continuous succession throu h all of said'laminae vin each cell said cells belng disposed between an optical 'polarizer and an analyzer.

15. In an apparatus for the electrical transmission of pictures or the like, means for de-composing and respectively re-composing the picture comprising light controlling cells, each cell consisting of a plurality of thin laminae-of a transparent medium variable as to itsoptical 'roperties by the application of an electrica potential, and means for varying said properties in continuous succession through all of said laminae in each cell said cells being disposed between two artificial crystals of sodium nitrate serving as optical polarizers and analyzers.

16. In anapparatus -for the electricaltransmission of pictures or the like, means for de-composing and respectively re-composing the picture comprising a pair of light controlling cells each at the transmitting and at t e receiving station, each cellconsisting of a lurality of'thin laminae of -'a' trans: parent, medium variable as to its optical properties by the application'of an electric potental, and means for varying said properties in continuous succession through all of said laminae in each cell, the cells at the cei'vin station l transmitting station servingjto de-compose the picture into individualelements and. the cells at the receiving station serving to re compose it, and means for synchronously controlling the application of electric poten-- this to said cells 'at the transmitting and re- 17.. nan apparatus for the electrical trans.-

within the range to which the missionof or the like, means for decomposing and respectively 're-composing the picture comprising corresponding light controlling cells each at the transmittin and at the receiving station, of a pluralityof thinlaminae of a transpar- 4 cut medium variable as to'its optical properties in accordance with the frequency of electric potential applied thereto, each each cell consisting laminabeing res nsive to a d1fi'erent m frequency, means or applying in continuous succession to each cell the frequencies group of laminae contained in the cell is responsive, and electric connection between said stations e0 including a carrier wave generated at the transmitting" station and modulated in accordance with the control frequencies applied to the cell at that station, for applying corre-' sponding control frequencies synchronously 86 to the corresponding cells at the receiving station.

18. In an apparatus for' the electrical transmission of pictures or the likein combination light control cells'at the transmit- 90 ting station each consisting of laminated elements, of a transparent medium whose optical properties are variablein accordance with articular electric control .impluses applied plcture into elementary light impulses of different intensity, means for'converting said light impulses into elementary electric impulses, means for transmitting said elementary electric impulses to the receiving station, similarly constructed cells at the receiv' station for re-com gthe picture, a a source of light at e receiving station whose beam is controlled by said cells, means for synchronously appl to the cells at the receiving station the ectrical control impulses applied to the corresponding cells at to it for spacially de-composing the as the transmitting station, and means. for applying to the receiving station cells simultaneously the received elementary electric impulses representing 'the .de-composed picture to causethe receiving station cells i to specially re-compose the picture from the elementary electric impulses received and to control thejntensity of the local light beam passing through said cells in accordance with the intensity-of the individual elementa electric impulses received to give eac spacially 'relaced picture element its proper light intensity.

19. In an apparatus for the electrical.

transmission of pictures or the like, means .for de-composing and repectively re-composing the picture, comBri ing light controlling m s e mitting and at the receiving station, the cells at the transmitting station se for 119- composing the picture into individual ele-h mentary-light impulses of difierentintensity,

mean for; said impulses -into ele- 1 v co p na the tree ".m

mentary electric impulses and means for transmitting saidimpulses to the receiving station, the cells at the receiving station serving for spacially re-composing the picture, each of the aforementioned cells consisting of a plurality of thin laminae of a transparent medium'variable as to its optical properties in accordance with the frequency of electric potential applied thereto, each lamina being responsive to a different frequency means for applying in continuous succession to each cell the frequencies Within the range to which the group of laminae contained in the cell is responsive, electrical connection between said station for applying corresponding control frequencies synchronously to the corresponding cells atthe two stations, the cells at the receiving station being also optically responsive in accordance, with the elementary electric impulses received from the transmitting station, and a local source of light at the receiving station whose beam is controlled by said receiving cells in accordance with the varying intensity of said received elementary electric impulses to give each specially re-placed picture element its proper light intensity.

20. In an apparatus for. the electrical transmission of pictures or the like, means for de-composing and respectively re-composing the picture, consisting of a pair of cells each composed of laminae extending in the direction of the picture rays and whose individual optical transparancy is responsive to particular electric conditions applied to each lamina, the laminatio of one cell being disposed at an angle to-t lamination of the other cells, so that in the direction of the rays the apparent cross-lamination divides the picture into a plurality of spacially defined elements, means for cyclically applying in each cell successively to each lamina the electrical condition which render it transparent, the number of cycles per time unit applied to one cell being the nth multiple of the number of cycles applied to the other cell if n equals the number of laminae in said other cell. c

In testimony whereof I afiix m signature.

OTTO VON R NK. 

